Liquid crystal display having additional capacitors formed from pixel electrodes and a method for manufacturing the same

ABSTRACT

A liquid crystal display having an improved display characteristic and having a ring-structured storage capacitor of an independent wiring type wherein disconnection and/or short circuit defects are reduced and a method for manufacturing the same. The liquid crystal display has one or a plurality of first electrodes within each pixel region, for forming one or a plurality of auxiliary capacitors in conjunction with the opposing pixel electrode. The first electrodes surround the pixel electrodes in a ring type structure, and are connected to each other between adjacent pixel portions by at least one wiring connecting portion. The first electrodes are driven independently from the scanning signal lines and the display signal lines. Forming the first electrodes of the capacitors as independent wiring type having a ring structure simplifies the manufacturing process and utilizes the maximum pixel area. Also, the degree of freedom concerning the selection of the driving pulse signal of the liquid crystal display is improved to reduce the R-C delay.

BACKGROUND OF THE INVENTION

The present invention relates to a liquid crystal display and a methodfor manufacturing the same, and more particularly to an active matrixliquid crystal display wherein the display characteristics thereof areimproved by an increase in the aperture ratio and a reduction of thecapacitance of the gate wiring, and to a method for manufacturing thesame.

The present invention is an improvement over the invention which is thesubject matter of the present inventors' co-pending U.S. patentapplication Ser. No. 08/070,717 which was filed on Jun. 1, 1993, thedisclosure of which is hereby incorporated into this application byreference.

In response to a demand for personalized, space-saving displays whichserve as the interface between humans and computers (and other types ofcomputerized devices), various types of fiat screen or fiat paneldisplays, such as a liquid crystal display (LCD), a plasma display panel(PDP), an electroluminescent (EL) display, etc., have been developed toreplace conventional display devices, particularly a cathode-ray tube(CRT) which is relatively large and obtrusive. Among these fiat paneldisplay types, the progress of LCD technology attracts the mostinterest. In some forms, LCDs match or surpass the color picture qualityof CRTs.

Liquid crystal displays can have a simple matrix form or an activematrix form, using an electro-optic property of the liquid crystal whosemolecular arrangement is varied according to an electric field. Inparticular, the LCD in the active matrix form utilizes a combination ofliquid crystal technology and semiconductor technology, and isrecognized as being superior to CRT displays.

The active matrix LCDs utilize an active device having a non-linearcharacteristic in each of a plurality of pixels arranged in a matrixconfiguration, using the switching characteristic of the device tothereby control each pixel. One type of the active matrix LCD embodies amemory function through an electro-optic effect of the liquid crystal. Athin film transistor (hereinafter referred to as a "TFT") having threeterminals is ordinarily used as the active device, or a thin film diode(TFD), for example, a metal insulator metal type (MIM) having twoterminals, is used. In the active matrix LCD which utilizes such activedevices, millions or even billions of pixels are integrated on a glasssubstrate together with pixel address wiring, to thereby provide amatrix driver circuit, with the TFTs serving as switching elements.

However, in the active matrix LCD whose display has a large screen andhigh definition, the number of the pixels increases. Accordingly, theaperture ratio of the individual pixels is decreased, therebyconcomitantly reducing the brightness of the LCD.

In the meantime, in the above active matrix LCD, a capacitance (Cgd)results between the gate and drain electrode of the TFT. When the signalof the gate pulse is changed from "High" to "Low", the potential of tilepixel electrode is lowered due to tile effect of the above capacitanceCgd. This lowering potential change is conventionally referred to as"offset voltage". When the offset voltage is applied to the liquidcrystal as a direct voltage, an unfavorable phenomenon such as imagesticking, flicker generation etc., occurs. Therefore, reducing such anoffset voltage is necessary, as by forming an auxiliary capacitor inparallel with the liquid crystal cell.

Further, to obtain uniformity of an image displayed on the active matrixLCD, it is necessary that the voltage of a first signal applied througha data line in a writing operation is held constant for a certain timeuntil a second signal is received. Also, in order to improve the imagequality of the display, an auxiliary capacitor is formed in parallelwith a liquid crystal cell. When the writing operation to the LCD isperformed at a frequency of 60 Hz, the retaining duration is 16.7milliseconds. The time constant, which is determined by the resistanceof the liquid crystal and the dielectric constant thereof, must besufficiently large with respect to the above values.

The auxiliary capacitor in parallel with the liquid crystal cell may beformed in two ways; that is, as an additional-capacitance type (Ca type)cell or as a storage capacitance type (Cs type) cell.

FIG. 1 shows a pixel layout of a conventional liquid crystal display onwhich the additional capacitance type storage capacitor is formed andFIG. 2 is a cross-sectional view taken along line II--II of FIG. 1.

In FIG. 1, a single pixel region and portions of adjacent pixel regionssurrounding it, are illustrated. In a complete LCD display, rows of anumber of gate lines 1 and orthogonal columns of a number of data lines5a are arranged in a matrix configuration. Thus, a pixel is formed inthe regions bounded by these two kinds of lines. In each pixel region,an additional-capacitance type capacitor Ca, a thin film transistor(TFT) as a switching device, a light transmissive portion (aperturearea), a transparent pixel electrode 4 and a color filter layer 21 areprovided. Gate line 1 and data line 5a are referred to as a scanningsignal line and a display signal line, respectively.

As can be seen in FIG. 1, the first electrode 10 of eachadditional-capacitance type capacitor Ca is formed as a tab-like portionprojected into a respective pixel portion from the scanning signallines 1. Similarly, the gate electrode G of each TFT is also formed asan integral tab-like portion projected into a respective pixel portionfrom the scanning signal lines 1 (in the opposite direction to thecorresponding first electrode of the capacitor). Each TFT systemcomprises a semiconductor layer 3 formed over a gate electrode G, atab-like perpendicularly protruding portion of display signal line 5a(drain electrode) adjoining the left end of semiconductor layer 3, asource electrode 5b adjoining the right end of semiconductor layer 3 anda transparent pixel electrode 4. Transparent pixel electrode 4 iscomprised of a transparent conductive material such as indium tin oxide(ITO).

All of the scanning signal lines 1, display signal lines 5a, capacitorsCa, TFTs, and pixel electrodes 4 are formed as part of a multilayerstructure formed on the inner surface of a rear glass substrate 100, ascan be seen in FIG. 2.

The process for forming the LCD having the additional-capacitance typecapacitors Ca is explained in more detail as follows. First electrode 10of each auxiliary capacitor Ca and each scanning signal line 1 aresimultaneously formed by appropriately patterning an opaque conductivematerial (e.g., of aluminum, chromium, molybdenum, or tantalum)deposited on the inner surface of the rear glass substrate 100 via aconventional photolithography process. Thereafter, an insulating layer 2is formed over the scanning signal lines 1, first electrodes 10 ofcapacitors Ca and the exposed regions of the inner surface of the rearglass substrate 100 as shown in FIG. 2. Next, the display signal lines5a and transparent pixel electrodes 4 are separately formed, e.g., bysuccessive photolithography processes. Then, a protective layer 6 isformed over pixel electrodes 4, display signal lines 5a, and the exposedregions of insulating layer 2, to thereby complete the multilayerstructure provided on the inner surface of the rear glass substrate 100.

With reference to FIG. 2, the prior art active matrix LCD furtherincludes a front glass substrate 101 having a multilayer structureformed on the inner surface thereof, and oriented parallel to the rearglass substrate 100. For example, a light shielding layer (black) matrix20 for light shielding is formed on the inner surface of front glasssubstrate 101. Light shielding layer matrix 20 is formed byappropriately patterning a light-shielding layer via a conventionalphotolithography process, to define an aperture area occupying most ofeach pixel electrode 4 arranged on rear glass substrate 100. Thereafter,a color filter layer 21 is formed over light shielding layer matrix 20and the exposed areas of the inner surface of the front glass substrate101. The color filter layer 21 includes light transmissive portions 21adisposed in the aperture areas. Next, a protective layer 22 is formedover the color filter layer 21. Then, a transparent electrode 23 isformed over protective layer 22, to thereby complete the multilayerstructure provided on the inner surface of the front glass substrate101.

It can be noted that the conventional active matrix LCD further includesa thin layer of liquid crystal sandwiched between the front glasssubstrate 101 and the rear glass substrate 100, and disposed in contactwith transparent electrode 23 and protective layer 6. Subsequent processsteps well-known to those of ordinary skill in the pertinent art arethen carried out to fix front glass substrate 101 and rear glasssubstrate 100 using a conventional sealant (not shown), and the liquidcrystal is injected and sealed within the cavity formed therebetween.

In the active matrix LCD of the additional capacitance type, since firstelectrodes 10 of the additional-capacitance type capacitors and scanningsignal lines 1 are simultaneously patterned using the same material, anadditional process is unnecessary. Accordingly, the process for makingthe active matrix LCD can be simplified.

However, based upon tile foregoing description of the conventionalactive matrix LCD, it should also be appreciated that tile prior artsuffers from certain drawbacks, as follows. Because the first electrode10 of each capacitor Ca is formed of an opaque metal, and further,because the first electrode 10 of each capacitor Ca overlaps asignificant portion of its associated pixel electrode 4, the aperturearea of each pixel is significantly reduced by the corresponding overlaparea, thereby reducing the aperture ratio thereof.

Moreover, since the display signal lines 5a and pixel electrodes 4 areformed together on the same insulating layer 2, they must be separatedby a predetermined distance so as to achieve electrical isolationtherebetween. This reduces the aperture area of the LCD and thus lowersthe contrast ratio and luminance of the LCD.

Additionally, since the first electrode 10 of the additional capacitanceis connected to tile scanning signal line 1, i.e. the gate line, thewiring capacitance of the scanning signal line is much increased.Therefore, the load is increased when operating tile scanning signalline, to increase the propagation delay time of the gate pulse signal,i.e. the gate delay.

FIG. 3 is an equivalent circuit diagram of the LCD device of theconventional additional-capacitance type as shown in FIGS. 1 and 2. Intile unit pixel area defined by the scanning signal line 1 and thedisplay signal line 5a, there exist capacitances such as the capacitance(Ccr) formed at the crossing portion of the scanning signal line 1 andtile display signal line 5a, the capacitance (Cadd) formed between thepixel electrode 4 and the first electrode 10 of theadditional-capacitance type capacitor Ca, the capacitance (Clc) formedbetween the pixel electrode 4 and the liquid crystal, the capacitance(Cds) formed between the source and drain electrodes of the thin filmtransistor, the capacitance (Cgs) formed between the gate and sourceelectrodes and the capacitance (Cgd) formed between the gate and drainelectrodes.

FIG. 4 is a layout of a pixel of a liquid crystal display which has anindependent wiring type storage capacitance type capacitor Cs formed inparallel with the liquid crystal cell, as another prior art method forforming the auxiliary capacitor. FIG. 5 is a cross-sectional view takenalong line IV--IV of FIG. 4, and shows only the lower part of the liquidcrystal display panel. Here, like reference numerals as those of FIG. 1and FIG. 2 represent the same elements.

There has been proposed an active matrix LCD of the storage capacitancetype which has an additional light shielding layer which reduces thelight leakage and has an independent wiring type storage capacitor so asto improve the characteristics of a display (see "High-Resolution10.3-in Diagonal Multicolor TFT-LCD," M. Tsumura, M. Kitajima, K.Funahata et al., SID 91 DIGEST, pp. 215-218).

In the active matrix LCD disclosed in the above paper, in order toobtain a high contrast ratio and high aperture ratio, a double lightshielding layer structure is formed and the storage capacitor is formedby an independent wiring separately formed apart from the gate line, soas to improve the display characteristics of the LCD.

In the structure of the above double light shielding layer, a firstlight shielding layer is formed on a front glass substrate on which acolor filter is provided as in the prior art, and a second lightshielding layer is formed on a rear glass substrate on which the TFT isprovided. The LCD having such a double light shielding layer structureexhibits an aperture ratio which is improved by 6-20% over theconventional LCD having only the first light shielding layer. Also, thestorage capacitor utilizes a common electrode with the gate electrodeformed of aluminum whose resistance is only one-tenth that of chromium(Cr). Thereby, the propagation delay characteristics along the scanningsignal line is improved.

The LCD having the double light shielding layer structure and thealuminum common electrode still needs much improvement. Also, there isundesirably a reduction of the aperture ratio due to the usage of anopaque metal (aluminum) for forming the electrodes of the storagecapacitor associated with each pixel.

Moreover, the process for fabricating the second light shielding layerentails installing a light shielding layer before forming an insulatinglayer merely shielding light during the manufacturing of the TFTs,thereby necessitating additional process steps which unduly increase thecost and complexity of the LCD manufacturing process.

As shown in FIG. 4, an independent wiring storage capacitance typecapacitor Cs is a structure wherein a transparent,conductive materialsuch as indium-tin oxide (ITO) replaces the opaque metal, e.g., thealuminum, in the above-mentioned conventional TFT-LCD. The lightshielding layer structure formed around transparent pixel electrode 4 isnot illustrated in FIG. 4 because it is not essential. FIG. 4 shows onlypart of a large number of pixel portions defined by a large number ofscanning signal lines 1 and a large number of display signal lines 5a asshown in FIG. 1. Independent wiring storage capacitance type capacitorCst is separated from scanning signal lines 1, differently from theadditional capacitance type capacitor Ca shown in FIG. 1, so as to beconnected with the capacitor Cs in the adjacent pixel portion by anindependent wiring 11 formed as a different conductive layer.

As shown in FIG. 4, the LCD having the independent wiring storagecapacitance type capacitor utilizes the inversely staggered TFTs asswitching devices. If the forming process is observed, each gateelectrode G which is formed such that each of scanning signal lines 1 isformed with a tab-like portion projected into each pixel portion, eachfirst electrode 10a of each storage capacitor Cs and each independentwiring 11 which is an extension of the first electrode 10a are formed soas to be parallel to the rear glass substrate of the liquid crystaldisplay panel. Successively, after insulating layer 2 such as with asilicon nitride (SIN) layer is formed on the front surface, asemiconductor layer 3 and a transparent pixel electrode 4 are formed ina predetermined pattern, and then the display signal lines 5a and thesource electrodes 5b are formed thereon. Subsequent processes areaccomplished by a method conventionally used in the LCD field.

Since the liquid crystal display of the independent wiring storagecapacitance type capacitor as shown in FIGS. 4 and 5 utilizestransparent ITO for forming first electrode 10a of storage capacitor Cs,the aperture area does not decrease by as much as that of the opaqueelectrode type. Meanwhile, since the light shielding layer does notexist on the rear glass substrate of the liquid crystal display panelalongside the pixel electrode, the contrast ratio of the LCD is reducedsignificantly and an additional process is required for forming firstelectrodes 10a of storage capacitors Cs. (This process is performed bydepositing an additional transparent conductive material such as ITOwhich is different from the opaque conductive material of the scanningsignal lines and then etching the transparent conductive material.)Moreover, the manufacturing yield thereof is disadvantageous since thecrossing portions of the wirings are increased when compared to the LCDas shown in FIG. 1.

FIG. 6 is an equivalent circuit diagram of the LCD device of theconventional auxiliary capacitor type as shown in FIGS. 4 and 5. In theunit pixel defined by the scanning signal line 1 and the display signalline 5a, there exist capacitances such as the capacitance (Ccr) formedat the crossing portion of the scanning signal line 1 and the displaysignal line 5a, the capacitance (Cst) formed between the pixel electrode4 and the first electrode 10a of the opposing storage capacitor Cs, thecapacitance (Clc) formed between the pixel electrode 4 and the liquidcrystal the capacitance (Cds) formed between tile source and drainelectrodes of the thin film transistor, the capacitance (Cgs) formedbetween the gate and source electrodes and the capacitance (Cgd) formedbetween the gate and drain electrodes.

In the LCD of the independent wiring storage capacitance type as shownin FIGS. 4 to 6, the capacitance of the gate wiring (Cin) may becalculated by the following equation (1).

    Cin=Ccr+Cgs+1/[(1/Cgd)+{1/(Clc+Cst)}]                      (1)

In the meantime, in the LCD of the additional capacitance type as shownin FIGS. 1 to 3, the capacitance of the gate wiring (Cad) may becalculated by the following equation (2).

    Cad=Cin+1/[(1/Cst)+{1/(Clc+Cgs)}]                          (2)

From the comparison of the above equations (1) and (2), the gate linecapacitance of an additional capacitance type LCD is several times asmuch as that of a storage capacitance type LCD. Therefore, whenoperating the gate line of the additional capacitance type LCD, the loadthereof is increased, which increases the gate delay.

From the above, although the manufacturing process of the additionalcapacitance type LCD is simplified, obtaining a uniform image isdifficult due to the gate delay since the gate wiring capacitance islarge. In the meantime, the gate wiring capacitance of the storagecapacitance type LCD is small. However, forming the first electrode oftile storage capacitor using an opaque metal, which simplifies themanufacturing process thereof, also lowers the aperture ratiosignificantly. Forming the first electrode of the storage capacitorusing a transparent material improves the aperture ratio, butnecessitates an additional process. Both the auxiliary capacitor typeLCDs have many crossing points of the wiring layers, which increases thepossibilities for discontinuity defects or short circuiting of thewiring.

To improve the problems exhibited in the above-mentioned liquid crystaldisplay of the additional capacitance type (FIGS. 1 to 3) and in that ofthe independent wiring storage capacitance type (FIGS. 4 to 6), S. S.Kim et. al (including one of the present inventors) have described aninvention wherein the LCD includes a storage capacitance type capacitorstructured with a ring electrode which faces a corresponding transparentpixel electrode and encloses the transparent pixel electrode in a ring,as filed on Aug. 25, 1992 as U.S. patent application Ser. No. 07/934,396which is now U.S. Pat. No. 5,339,181.

The LCD disclosed in U.S. Pat. No. 5,339,181 will be explained belowwith reference to FIGS. 7 and 8. Here, the same reference numerals asthose of FIGS. 1, 2, 4 and 5 represent the same components.

As can be seen from a comparison of FIG. 7 with FIGS. 1 and 4, theactive matrix LCD shown in FIG. 7 is manufactured according to theconventional method except for the fact that the layout of firstelectrodes 10 of storage capacitors (i.e. storage capacitance typecapacitors) Cs associated with each pixel electrode 4 is changed so thatthe first electrode 10 is arranged in the peripheral region of the pixelelectrode 4 to thereby increase the aperture ratio and contrast ratio ofthe LCD as compared with the conventional LCD. In more detail, theopaque metal layer from which the display signal lines 5a and the firstelectrodes 10 of storage capacitors Cs are formed is patterned in amanner such that the first electrodes 10 of storage capacitors Cssubstantially surround their associated pixel electrodes 4, andpreferably, overlap (i.e., underlay) only a peripheral edge portionthereof. As can be seen more clearly in FIG. 8 (taken along line VI--VIof FIG. 7), the first electrode 10 of the capacitor Cs is disposedsubstantially beneath the matrix of the light shielding layer 20provided on the inner surface of the front glass substrate 101, and doesnot extend into the envelope of the aperture area, thereby significantlyincreasing the aperture ratio compared with conventional active matrixLCDs.

Additionally, the first electrode 10 of each capacitor Cs formed alongthe periphery of each corresponding pixel electrode 4, serves as anadditional light shielding layer, as illustrated in FIG. 8. That is, thefirst electrode 10 minimizes the amount of leakage light passing throughthe aperture area of the front glass substrate 101 from the region ofthe liquid crystal located outside of the envelope of the aperture area.

In the case of the conventional active matrix LCD depicted in FIG. 2, itcan be seen that any extraneous light entering the front glass substrate101 at an angle of incidence greater than Θ₁ is emitted through theaperture area of the front glass substrate 101. In the case of the LCDof U.S. Pat. No. 5,339,181, only extraneous light which enters the frontglass substrate at an angle of incidence greater than Θ₂ is emittedthrough the aperture area of the front glass substrate as illustrated inFIG. 8. Excess light (or "leakage light") which strikes the front glasssubstrate whose angle is less than the angle of incidence Θ₂ is blockedby first electrode 10 of the adjacent storage capacitor. Thus, relativeto the aforesaid prior art active matrix LCDs, the LCD of the U.S. Pat.No. 5,339,181 reduces the amount of leakage light emitted through theaperture area of front glass substrate 101 by an amount which isproportional to the difference between Θ₂ and Θ₁, thereby significantlyincreasing the contrast ratio.

Meanwhile, the liquid crystal display having the ring type electrodestorage capacitor represents an improvement in display characteristics,i.e., a better aperture ratio, increased contrast ratio, etc. However,due to the introduction of foreign matter or in case of a weakinsulating film at wiring crossings (the intersection of scanning signallines 1 and display signal lines 5a), wiring fractures in scanningsignal lines 1 and/or short circuits between scanning signal lines 1 anddisplay signal lines 5a may occur, to thereby significantly lower theyield of manufactured liquid crystal displays.

In order to solve the problems of wiring fractures in scanning signallines 1 and/or short circuits between scanning signal lines 1 anddisplay signal lines 5a without reducing the aperture ratio and thecontrast ratio, co-pending U.S. patent application Ser. No. 08/070,717describes an invention wherein each row of adjacent first electrodes ofthe capacitors are electrically connected together using redundancyconnecting conductors or wherein the LCD has duplicated scanning signallines associated with each pixel and electrically connected to the firstelectrode of the capacitor.

FIG. 9 shows a pixel layout of a liquid crystal display according to oneembodiment of the invention disclosed in the above U.S. patentapplication Ser. No. 08/070,717. Here, the same reference numerals asthose of FIGS. 1 to 8 represent the same components.

Referring to FIG. 9, the liquid crystal display is the same as thathaving a ring-structured capacitor electrode as shown in FIG. 7 exceptthat a redundancy connecting portion 12 is formed between the firstelectrodes 10 of the storage capacitors which are formed in each pixelregion in a manner such that the first electrodes 10 of storagecapacitors Cs substantially surround their associated pixel electrodes4. Redundancy connecting portions 12 which are connected between thefirst electrode 10 of each one of the storage capacitors aresimultaneously formed with a pattern of the first electrodes 10 andintersects display signal lines 5a with a dielectric film interposedtherebetween.

FIG. 10 shows a pixel layout of a liquid crystal display according toanother embodiment of the invention disclosed in the above U.S. patentapplication Ser. No. 08/070,717. Here, the same reference numerals asthose of FIGS. 1 to 8 represent the same components.

Referring to FIG. 10, the liquid crystal display is the same as thathaving a ring-structured capacitor electrode as shown in, FIG. 7. Theliquid crystal display shown in FIG. 10 is characterized by having itsscanning signal lines duplicated as first scanning signal lines 1a andsecond scanning signal lines 1b as compared with the pixel layout of theliquid crystal display shown in FIG. 7 as described above. A pluralityof the scanning signal lines which are each constituted by an electrodepair of a first scanning signal line 1a and a second scanning signalline 1b are arranged at predetermined intervals. Here, the pixelportions are defined within first and second scanning signal lines 1aand 1b and display signal lines 5a.

Moreover, as compared with FIG. 7, the thin film transistor TFT,employed as a switching device, is not formed on an integral protrudingtab-like portion of a corresponding scanning signal line 1 but rather isformed on first scanning signal line 1a. That is, a gate electrode ofthe thin film transistor is rotated 90° so as to be consistent withfirst scanning signal line 1a, thereby to maximize the aperture ratio ofthe liquid crystal display.

In the above liquid crystal display as shown in FIGS. 9 and 10, theredundancy connecting portions for connecting the first electrodes ofthe capacitors or the two-fold scanning signal lines are formed by asimple change of the pattern layout without requiring an additionalprocess. The first electrode is formed to be a ring-type which canutilize a maximum pixel area, thereby enhancing the aperture ratio ofthe LCD. Since the first electrode of the storage capacitor serves as anadditional light shielding layer, the contrast ratio is greatlyenhanced.

Additionally, a redundancy connecting portion is formed for connectingthe first electrodes of the capacitors to each other, or the scanningsignal lines are doubled, so that disconnection and shorting defects ofthe scanning signal lines in the crossing portions of the wirings can bedecreased and repaired. For example, referring to FIG. 10, adisconnection defects occurs with respect to one display signalelectrode 5a when disconnections occur at the crossing portions with offirst and second scanning signal electrodes 1a and 1b, but not when adisconnection occurs either with first scanning signal electrode 1a orwith second scanning signal electrode 1b. In the meantime, when a shortcircuit occurs between either of the scanning signal electrodes 1a and1b and the display signal electrode 5a, the shorting defects may berepaired by cutting the signal line on both sides of the crossingportion where the short circuit has occurred. Since the scanning signalelectrode is duplicated, the shorting defect may be easily repaired.

SUMMARY OF THE INVENTION

It is a first object of the present invention to provide a liquidcrystal display having an independent wiring storage capacitance typewherein the display characteristic is improved.

It is a second object of the present invention to provide a liquidcrystal display having a ring-structured storage capacitor of anindependent wiring type wherein disconnection and/or shorting defectsare reduced.

It is a third object of the present invention to provide a method formanufacturing a liquid crystal display which is suitable formanufacturing the above liquid crystal display devices.

It is a fourth object of the present invention to provide a liquidcrystal display wherein the RC time constant is reduced to obtain auniform image.

It is a fifth object of the present invention to provide a method formanufacturing a liquid crystal display which is suitable formanufacturing the above liquid crystal display device.

In order to accomplish the first and second objects of the presentinvention, there is provided a liquid crystal display device comprising:

a transparent substrate;

a plurality of scanning signal lines and intersecting display signallines arranged in a matrix configuration on a surface of the transparentsubstrate, to thereby define a plurality of pixel regions each boundedby a pair of scanning signal lines and a pair of display signal lines;

a pixel electrode in each pixel region;

a switching device in each pixel region and connected with acorresponding display signal line and the pixel electrode; and

a ring-type first electrode disposed within each pixel region so as toface the corresponding pixel electrode and surround the pixel electrode,for forming a storage capacitance type capacitor with the pixelelectrode, the first electrodes of adjacent pixel portions beingconnected to each other by at least one wiring connecting portion, thefirst electrode being driven independently from the scanning signallines and the display signal lines.

The first electrodes of the storage capacitors preferably are comprisedof the same material as the bonding pads for connecting the scanningsignal lines and the display signal lines to an outer driving circuitand simultaneously patterned when forming the bonding pads.

According to one embodiment of the present invention, the firstelectrodes of the storage capacitors and the scanning signal lines arecomprised of the same material and simultaneously patterned. Thepatterned first electrodes of the storage capacitors and the scanningsignal lines may be formed by using an opaque conductive metal such asaluminum, chromium, molybdenum or tantalum. The first electrodes of thestorage capacitors and the scanning signal lines may be formed so as tohave a stacked structure comprised of at least two metals.

The connecting portion for connecting the first electrodes of theadjacent storage capacitors is formed so as to cross the display signallines. Preferably, the connecting portions between two first electrodesof adjacent capacitors are duplicated.

According to another embodiment of the present invention, the firstelectrode of the storage capacitors and the scanning signal lines areformed from different conductive layers. The wiring connection portionis preferably formed so as to cross the scanning signal lines. The firstelectrodes of the storage capacitors and the scanning signal lines areisolated from each other by interposing an insulating layertherebetween. The connecting portions between first electrodes of theadjacent two capacitors are preferably duplicated.

According to one embodiment of the present invention, the switchingdevice is a thin film transistor comprising:

a gate electrode formed of a portion of each scanning signal line;

a drain electrode formed of a projecting portion of each display signalline;

a source electrode overlapping a portion of each pixel electrode; and

a semiconductor layer formed on an insulating layer on the gateelectrode, and patterned to connect the drain electrode to the sourceelectrode.

The thin film transistor is preferably an inversely staggered typeformed on a crossing point of the scanning signal lines and the displaysignal lines. The gate electrode, drain electrode and semiconductorlayer of the thin film transistor are preferably formed outside theboundary of the pixel electrode.

Preferably, the source electrode of the thin film transistor overlays aportion of the first electrode of the storage capacitor. The firstelectrode of the storage capacitor partially overlaps along the overallperiphery of the pixel electrode. One portion of a periphery of thefirst electrode of the storage capacitor overlaps one portion of thepixel electrode by a predetermined width without abrupt steps.

In another embodiment of the present invention, the switching device isa thin film diode.

The first electrode of the storage capacitor and the scanning signallines are preferably formed on a first horizontal plane and the pixelelectrode and the display signal lines are formed on a second horizontalplane, the first and second horizontal planes being spaced apart frowneach other by an insulating layer interposed therebetween.

Also, the present invention provides a liquid crystal displaycomprising:

a front glass substrate having inner and outer surfaces;

a rear glass substrate having inner and outer surfaces, parallel to thefront glass substrate and separated therefrom by a predetermineddistance to allow its inner surface to oppose the inner surface of thefront glass substrate;

a plurality of scanning signal lines and intersecting display signallines arranged on the inner surface of the rear glass substrate inmatrixes for defining a plurality of pixel areas each bounded by a pairof the scanning signal lines and a pair of the display signal lines;

a pixel electrode within each pixel area;

a switching device within each pixel area for connecting a correspondingone of the display signal lines to the pixel electrode;

a ring type first electrode arranged within each pixel area andoppositely enclosing the pixel electrode to form a capacitor inconjunction with the pixel electrode, the first electrodes of adjacentpixel areas being connected by at least one wiring connecting portionand the first electrode being driven independently from the scanningsignal lines and the display signal lines;

a light-shielding layer matrix on the inner surface of the front glasssubstrate aligned with each pixel area for defining a light-transmittingaperture area therein;

a color filter layer on the inner surface of the front glass substrateand including a light transmitting area covering the light-transmittingaperture area and the light-shielding layer; and

a transparent electrode formed on the color filter layer;

A first protective layer is preferably sandwiched between the colorfilter layer and the transparent electrode and a second protective layercovers the inner surface of the rear glass substrate.

The border of the aperture area defined by the periphery of thelight-shielding layer of each pixel region is substantially in verticalalignment with an inner periphery of the first electrode of the storagecapacitor, whereby the first electrode of the storage capacitorfunctions as a secondary light shielding layer for decreasing lightleakage, being other than the light permitted to be passed through theaperture area. Light entering the aperture area via the rear glasssubstrate defines a virtual aperture area, and the first electrodes ofthe storage capacitors do not extend into the virtual aperture area.

To achieve the third object of the present invention, there is provideda method for manufacturing a liquid crystal display, having atransparent substrate; a plurality of scanning signal lines andintersecting display signal lines arranged in a matrix configuration ona surface of the transparent substrate to thereby define a plurality ofpixel regions each bounded by a pair of scanning signal lines and a pairof display signal lines; a pixel electrode in each pixel region; aswitching device in each pixel region; and a first electrode within eachpixel region being independent from the scanning signal lines and thedisplay signal lines, the method comprising the steps of:

forming a first metal layer on a transparent substrate;

patterning the first metal layer to form bonding pads for connectinginner elements to an outer circuit;

forming a second metal layer on the resultant structure having thebonding pads thereon;

patterning the second metal layer to form a plurality of scanning signallines in a regular arrangement, a first electrode of a storagecapacitance type capacitor disposed in each pixel area, and at least onewiring connecting portion for connecting first electrodes of adjacentstorage capacitance type capacitors, the first electrodes beingindependent of the scanning signal lines and the display signal lines;

successively forming an insulating layer and a semiconductor layer onthe surface of the resultant structure;

patterning the semiconductor layer to leave the semiconductor layer onlyaround a portion of the scanning signal lines;

forming a transparent conductive layer on the surface of the resultantstructure;

patterning the transparent conductive layer to form a pixel electrodeopposed to the first electrode of the storage capacitance type capacitoralong a periphery thereof;

forming a third metal layer on the resultant structure; and

patterning the third metal layer to form the plurality of display signallines regularly arranged while intersecting the scanning signal lines,and source and drain electrodes of a thin film transistor on thesemiconductor layer.

According to one embodiment of the present invention, the scanningsignal lines and the first electrodes of the storage capacitance typecapacitors are preferably formed simultaneously by patterning the secondmetal layer. In such a case, the wiring connection portion is formed sothat the first electrodes of the storage capacitors are connected inparallel with the scanning signal lines.

According to another embodiment of the present invention, the scanningsignal lines and the first electrodes of the storage capacitance typecapacitors may be formed by a separate patterning process.

In the present invention, the wiring connection portions may be formedso as to cross the scanning signal lines.

Further, the third object of the present invention can be achieved byproviding a method for manufacturing a liquid crystal display having atransparent substrate; a plurality of scanning signal lines andintersecting display signal lines arranged in a matrix configuration ona surface of the transparent substrate to thereby define a plurality ofpixel regions each bounded by a pair of scanning signal lines and a pairof display signal lines; a pixel electrode in each pixel region; aswitching device in each pixel region; and a first electrode within eachpixel region being independent from the scanning signal lines and thedisplay signal lines, the method comprising the steps of:

forming a first metal layer on a transparent substrate;

patterning the first metal layer to form bonding pads for connectinginner elements to an outer circuit and to also form a plurality of firstelectrodes of a storage capacitance type capacitor in each pixel areaand to form at least one wiring connecting portion for connecting firstelectrodes of adjacent storage capacitance type capacitor, the firstelectrode being independent from the scanning signal lines and thedisplay signal lines;

forming a second metal layer on the resultant structure having thebonding pads and the first electrodes of the capacitors thereon;

patterning the second metal layer to form the scanning signal lines atregular intervals;

successively forming an insulating layer and a semiconductor layer onthe surface of the resultant structure;

patterning the semiconductor layer to leave the semiconductor layer onlyaround a portion of the scanning signal lines;

forming a transparent conductive layer on, the surface of the resultantstructure;

patterning the transparent conductive layer to form a pixel electrodeopposed to the first electrode of the storage capacitance type capacitoralong a periphery thereof;

forming a third metal layer on the resultant structure; and

patterning the third metal layer to form the plurality of display signallines regularly arranged and intersecting the scanning signal lines, andto form source and drain electrodes of a thin film transistor on thesemiconductor layer.

To achieve the fourth object of the present invention, there is providedliquid crystal display device comprising:

a transparent substrate;

a plurality of first scanning signal lines and an intersecting pluralityof display signal lines arranged in a matrix configuration on thesurface of the transparent substrate, to thereby define a plurality ofpixel regions each bounded by a pair of first scanning signal lines anda pair of display signal lines;

a pixel electrode in each pixel region;

a switching device in each pixel region and connected with acorresponding display signal line and the pixel electrode of therespective pixel region;

a first electrode of an additional capacitance type capacitor withineach pixel region, for forming an additional capacitance type capacitorin conjunction with the pixel electrode thereof and arranged so as toface a portion of each pixel electrode with an insulating layerinterposed therebetween;

a first electrode of a storage capacitance type capacitor within eachpixel region formed by interposing an insulating layer, for forming astorage capacitance type capacitor in conjunction with the pixelelectrode thereof and arranged so as to face a portion of each pixelelectrode, the first electrode being independent from the scanningsignal lines; and

a plurality of first independent wires connecting the first electrodesof adjacent storage capacitance type capacitors.

The first electrode of the storage capacitance type capacitor and thefirst electrode of the additional capacitance type capacitor arepreferably formed using the same material as the scanning signal lines.In a preferred embodiment of the present invention, the first electrodeof the storage capacitance type capacitor is comprised of a conductivetransparent material.

According to a preferred embodiment of the present invention, thescanning signal lines are formed so as to have portions protruding intothe pixel regions so that the protruding portions partially overlap thepixel electrodes to form the first electrodes of the additionalcapacitance type capacitors.

According to one embodiment of the present invention, the firstelectrode of the storage capacitance type capacitor and the firstelectrode of the additional capacitance type capacitor are formed of asingle wiring type.

According to another embodiment of the present invention, the firstelectrode of the additional capacitance type capacitor is formed in aring surrounding the peripheral region of the pixel electrode, the firstelectrode of the additional capacitance type capacitor being formedbetween the scanning signal line for driving the pixel electrode of anadjacent pixel region and the first electrode of the storage capacitancetype capacitor. Preferably, at least one redundancy connection portionfor connecting the first electrode to the adjacent first electrode isformed.

According to still another embodiment of the present invention, thefirst electrode of the storage capacitance capacitor is formed in a ringtype surrounding the peripheral region of the pixel electrode, the firstelectrode of the storage capacitance type capacitor being formed betweenthe scanning signal line and the first electrode of the additionalcapacitance type capacitor. In such a case, a second independent wiringfor connecting the first electrodes of the storage capacitance typecapacitors is preferably formed.

The first electrode of the storage capacitance type capacitor may beformed using the same material as that of bonding pads formed on thetransparent substrate for connecting the scanning signal lines to anouter driving circuit.

In one preferred embodiment of the present invention, the ratio of thestorage capacitance with respect to the additional capacitance isgreater than 80:20.

The present invention provides a liquid crystal display devicecomprising:

a transparent substrate;

a plurality of first scanning signal lines and display signal linesarranged in a matrix configuration on a surface of the transparentsubstrate, to thereby define a plurality of pixel regions each boundedby a pair of first scanning signal lines and a pair of display signallines;

a pixel electrode in each pixel region;

a switching device in each pixel region and connected with acorresponding display signal line and the pixel electrode;

a first electrode of an additional capacitance type capacitor disposedwithin the pixel region so as to face the pixel electrode, for formingan additional capacitor with the pixel electrode with an insulatinglayer interposed therebetween, the first electrode of the additionalcapacitance type capacitor being formed in a ring shape which surroundsthe peripheral region of the pixel electrodes;

at least one redundancy connection portion for connecting the firstelectrodes of the additional capacitance type capacitors of adjacentpixel regions;

a first electrode of a storage capacitance type capacitor disposedwithin the pixel region so as to face the pixel electrode with aninsulating layer disposed therebetween, for forming a storage capacitorwith the pixel electrode, the first electrode being independent from thescanning signal lines, the first electrode of the storage capacitancetype capacitor being formed in a ring shape which surrounds theperipheral region of the pixel electrode, the first electrode of thestorage capacitance type capacitor being formed between thecorresponding scanning signal line and the first electrode of theadditional capacitance;

a first independent wiring connecting the first electrodes of thestorage capacitance type capacitors of adjacent pixel regions; and

a second independent wiring for connecting the first electrodes of thestorage capacitance type capacitors of adjacent pixel regions.

Also, the present invention provides a liquid crystal displaycomprising:

a front glass substrate having inner and outer surfaces;

a rear glass substrate having inner and outer surfaces, parallel to thefront glass substrate and separated therefrom by a predetermineddistance to allow its inner surface to oppose the inner surface of thefront glass substrate;

a plurality of scanning signal lines and display signal lines arrangedon the inner surface of the rear glass substrate as matrixes fordefining a plurality of pixel areas each bounded by means of a pair ofthe scanning signal lines and a pair of the display signal lines;

a pixel electrode within the pixel area;

a switching device within the pixel area for connecting a correspondingdisplay signal line to the pixel electrode;

a first electrode of an additional capacitance type capacitor disposedwithin the pixel region so as to face a portion of the pixel electrodewith an insulating layer interposed therebetween, for forming anadditional capacitance type capacitor;

a first electrode of a storage capacitance type capacitor disposedwithin the pixel region so as to face a portion of the pixel electrodewith an insulating layer interposed therebetween, for forming a storagecapacitance type capacitor with the pixel electrodes, the firstelectrode being independent from the scanning signal lines;

a light-shielding layer matrix formed on the inner surface of the frontglass substrate and aligned with each pixel area for defining alight-transmitting aperture area;

a color filter layer on the inner surface of the front glass substrateand including a light transmitting area covering the light-transmittingaperture area and the light-shielding layer;

a transparent electrode formed on the color filter layer; and

a liquid crystal layer between the front and rear glass substrate.

To achieve the fifth object of the present invention, there is provideda method for manufacturing a liquid crystal display having a liquidcrystal display having a transparent substrate; a plurality of scanningsignal lines and intersecting display signal lines arranged in a matrixconfiguration on a surface of the transparent substrate to therebydefine a plurality of pixel regions each bounded by a pair of scanningsignal lines and a pair of display signal lines; a pixel electrode ineach pixel region; a switching device in each pixel region; and a firstelectrode within each pixel region being independent from the scanningsignal lines and the display signal lines, the method comprising thesteps of:

forming a first metal layer on the transparent substrate;

patterning the first metal layer to form bonding pads for connectinginner elements to an outer circuit;

forming a second metal layer on the resultant structure having thebonding pads thereon;

patterning the second metal layer to form the scanning signal lines in aregular arrangement, a first electrode of additional capacitance typecapacitor within the pixel region so as to face a portion of the pixelelectrode, for forming an additional capacitance type capacitor with aninsulating layer interposed therebetween and a first electrode of astorage capacitance type capacitor disposed within the pixel region soas to face a portion of the pixel electrode, for forming storagecapacitors with the pixel electrodes with the insulating layerinterposed therebetween;

successively forming an insulating layer and a semiconductor layer onthe surface of the resultant structure;

patterning the semiconductor layer to leave the semiconductor layer onlyaround a portion of the scanning signal lines;

forming a transparent conductive layer on the surface of the resultantstructure;

patterning the transparent conductive layer to form a pixel electrode tooppose to the first electrode of the storage capacitor along a peripherythereof; and

forming a third metal layer on the surface;

patterning the third metal layer to form the plurality of display signallines regularly arranged while intersecting the scanning signal lines,and source and drain electrodes of a thin film transistor on thesemiconductor layer.

According to the present invention, the first electrodes of thecapacitor can be formed by a simple change of the pattern when formingthe scanning signal lines or when forming the bonding pads withoutrequiring an additional process, to thus simplify the process. Formingthe first electrode to be a ring-type electrode which can utilize themaximum pixel area, enhances the aperture ratio of the LCD. Furthermore,since the first electrode of the storage capacitor serves as anadditional light shielding layer, the contrast ratio and theeffectiveness of the light usage are greatly enhanced. Further, formingthe first electrodes of the storage capacitance type capacitors in anindependent wiring type improves the degree of freedom concerning theselection of the driving pulse signal of the liquid crystal display, andit reduces the R-C delay. Additionally, duplicating the connectingportions for connecting the first electrodes of the capacitors to eachother, can decrease and facilitates the repair of defects ofdisconnection and shorting of the driving lines for the first electrodesoccurring in the wiring crossing portions of the wirings, therebygreatly enhancing the yield of manufactured LCDs.

Further, in a liquid crystal display having the first electrodes of theadditional capacitance type and the first electrodes of the storagecapacitance type according to the present invention, the gate wiringcapacitance is decreased when compared to the liquid crystal displayhaving only the additional capacitance type capacitor so as to reducethe RC time constant.

BRIEF DESCRIPTION OF THE DRAWINGS

Further features and advantages will become more apparent from thefollowing and more particular description of the preferred embodiment ofthe invention as illustrated in the accompanying drawings in which thesame reference characters generally refer to like parts throughout theviews, and in which:

FIG. 1 is a pixel layout of a conventional liquid crystal display onwhich additional capacitance type capacitors are formed;

FIG. 2 is a cross-sectional view taken along line II--II of FIG. 1;

FIG. 3 is an equivalent circuit diagram of the LCD device of theconventional additional capacitance capacitor type as shown in FIGS. 1and 2;

FIG. 4 is a pixel layout of a conventional liquid crystal display havingindependent wiring-type storage-capacitance capacitors formed inparallel with the liquid crystal cells;

FIG. 5 is a cross-sectional view taken along line IV--IV of FIG. 4;

FIG. 6 is an equivalent circuit diagram of the LCD device of theconventional storage capacitance capacitor type as shown in FIGS. 4 and5;

FIG. 7 is a pixel layout of a liquid crystal display disclosed in U.S.Pat. No. 5,339,181;

FIG. 8 is a cross-sectional view taken along line VI--VI of FIG. 7;

FIG. 9 shows a pixel layout of a liquid crystal display according to oneembodiment of the invention disclosed in the above U.S. patentapplication Ser. No. 08/070,717;

FIG. 10 shows a pixel layout of a liquid crystal display according toanother embodiment of the invention disclosed in the above U.S. patentapplication Ser. No. 08/070,717;

FIG. 11 shows a pixel layout of a liquid crystal display according to afirst embodiment of the present invention:

FIG. 12 is a cross-sectional view taken along line D-D' of FIG. 11;

FIG. 13 is a cross-sectional view taken along line E-E' of FIG. 11;

FIG. 14 shows a pixel layout of the liquid crystal display according toa second embodiment of the present invention:

FIG. 15 is a schematic diagram showing an operational principle forexplaining the effect of the above second embodiment of the presentinvention;

FIG. 16 shows a pixel layout of a liquid crystal display according to athird embodiment of the present invention;

FIG. 17 is a cross-sectional view taken along line F-F' of FIG. 16;

FIG. 18 is an equivalent circuit diagram of the liquid crystal displayas shown in FIGS. 16 and 17:

FIG. 19 shows a pixel layout of the liquid crystal display according toa fourth embodiment of the present invention; and

FIG. 20 show a pixel layout according to a fifth embodiment of thepresent invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, the present invention will be explained in detail withreference to the accompanying drawings.

FIG. 11 shows a pixel layout of a liquid crystal display according to afirst embodiment of the present invention. Here, the same referencenumerals as in the foregoing drawings indicate the same components asthose in the foregoing drawings.

In FIG. 11, a single pixel region and portions of adjacent pixelssurrounding it, are illustrated. In a complete LCD, rows of a number ofscanning signal lines 1 and orthogonal columns of a number of displaysignal lines 5a are arranged in a matrix configuration. Thus, a pixel isformed in the regions bounded by these two kinds of lines. In each pixelregion, a storage capacitor Cs, a thin film transistor (TFT) as aswitching device, a light transmissive portion (aperture area), atransparent pixel electrode 4 and a color filter layer 21 (FIG. 13) areprovided. As can be seen in FIG. 11, a first electrode 10 of storagecapacitor Cs (as a storage capacitance type capacitor) is independentlyformed without being connected to scanning signal lines 5a so that itsurrounds a pixel electrode 4 in each pixel region. Further, theadjacent first electrodes 10 in adjacent pixel regions are connectedwith each other via the connection portions 14 in an independent wiringtype and are driven by another driving circuit different from that fordriving the scanning signal lines 1. Here, display signal line 5a iselectrically isolated from wiring connection portion 14 by interposingan insulating layer at a wiring crossing portion 16 where display signalline 5a crosses the wiring connection portion 14 between the adjacentfirst electrodes 10 of the storage capacitors.

In the meantime, an inversely staggered TFT using the scanning signalline 1 as a gate electrode is formed on scanning signal line 1 as aswitching device for applying an electrical signal to the pixelelectrode 4 via display signal line 5a, so that the pixel area ismaximized as much as possible. Instead of the inversely staggered TFT, athin film diode (TFD), for example, a metal insulator metal (MIM) diodehaving two terminals, may be used.

FIG. 12 is a cross-sectional view taken along line D-D' of FIG. 11. Withreference to FIGS. 11 and 12, one embodiment of a method formanufacturing a liquid crystal display according to the presentinvention will be explained below.

First, after preparing a rear glass substrate (not shown) of the liquidcrystal display, a pad metal layer is formed and then patterned to formbonding pads (not shown) in FIG. 12 for bonding display signal lines 5aand scanning signal lines 1 to a driving circuit. Here, the pad metallayer is formed by depositing chromium to a thickness of approximately2,000 Å. Thereafter, aluminum is deposited to a thickness of not morethan 4.000 Å on the front surface of the rear glass substrate, to form ametal layer; which is patterned to simultaneously form scanning signallines 1 and first electrodes 10 of the storage capacitors. The firstelectrode 10 of each storage capacitor, as shown in FIG. 11, is formedas a ring-type structure where the first electrode 10 is sufficientlyextended to the edge of the pixel region so as to utilize a maximumpixel region. Simultaneously, wiring connecting portions 14 are alsoformed so as to be connected between the first electrodes 10 of theadjacent capacitors. Here, each wiring connection portion 14 may beformed at the middle portion of first electrode 10 as shown in FIG. 11or at the edge portion thereof.

For simplifying the manufacturing process, first electrodes 10 of thestorage capacitors may be formed by using the same material as the padmaterial. That is, after forming the pad metal layer, the firstelectrodes 10 are simultaneously formed when patterning the pad metallayer. Alternatively, first electrodes 10 of the storage capacitors maybe formed via a different step from the step for forming the scanningsignal lines 1, by using a different metal from that used for scanningsignal lines 1.

Here, since first electrode 10 of the capacitor serves as a lightshielding layer described hereinafter, it should be comprised of anopaque conductive material. First electrode 10 may be formed in amultilayer structure or by using an alloy so far as it comprises anopaque conductive material.

Successively, when scanning signal lines 1 or first electrodes 10 aremade of aluminum, using an anodic oxide method, surfaces of theelectrodes can be covered by an aluminum oxide film (Al₂ O₃) whosethickness is not more than 2,000 Å, to enhance the electricalcharacteristics in the pixel electrode 4, crossing portion 16 and in theTFT.

Then, using a chemical vapor deposition (CVD) method, an insulatinglayer 2 comprising silicon nitride (SiNx) and a semiconductor layer 3comprising an amorphous hydride silicon (a-Si:H) are formed tothicknesses of about 3,000 Å or less and 2,000 Å or less, respectively.At this time, a-Si:H doped with an N-type impurity (n⁺ a-Si:H) isdeposited to form an ohmic layer having a thickness of approximately 500Å on the previously deposited a-Si:H. Thereafter, as shown in FIG. 11,the semiconductor layer 3 is patterned so as to define an area in whichthe switching devices will be formed on scanning signal lines 1 or theirnearby portions.

Successively, the insulating layer 2 on the bonding pads (not shown) isremoved, and a transparent conductive material, e.g., ITO, is depositedto a thickness of about 500 Å or less via a sputtering method, andpatterned to thereby form pixel electrodes 4. At this time, each pixelelectrode 4 is patterned to overlap the first electrode 10 of thestorage capacitor formed in the foregoing step by a predetermined width,with the insulating layer 2 being interposed therebetween. A capacitoris formed between the first electrode 10 of the storage capacitor andthe pixel electrode 4 on each pixel region by interposing the insulatinglayer 2 as a dielectric material therebetween, so that a voltage signalinput through display signal line 5a is maintained for a predeterminedtime period until the succeeding input signal arrives.

Then, chromium and aluminum are successively deposited on the wholesurface of the substrate to a thicknesses of about 500 Å or less and5,000 Å or less, respectively, via a sputtering method, and thenpatterned to form display signal lines 5a, sources 5b and the drainelectrodes of the TFTs. Thereafter, a protective layer 6 comprisingsilicon nitride is formed on the whole surface of the substrate to athickness of about 4,000 Å via a CVD method. Hence, fabrication of thelower substrate of the LCD is thereby completed.

FIG. 13 is a cross-sectional view taken along line E-E' of FIG. 11. Thelower panel of the LCD includes scanning signal lines 1 and the firstelectrodes 10 of the storage capacitors formed on the same horizontalplane on a rear glass substrate 100, a transparent insulating layer 2formed on the rear glass substrate 100 having the scanning signal lines1 and the first electrodes 10 already formed thereon, a pixel electrode4 formed in each pixel region so as to partially overlap the associatedfirst electrode 10 of the associated capacitor to a predeterminedextent, and a protective layer 6 formed thereon. Of course, onprotective layer 6, an orientation layer (not shown) is formed in asubsequent step for the orientation of the liquid crystal, which isconventional in the LCD art.

In the meantime the tipper panel of the LCD is formed in such a mannerthat, after the aperture area of the LCD is defined by forming a lightshielding layer 20 on the inner surface of the transparent front glasssubstrate 101 as matrices along the periphery of each pixel area. Thelight shielding layer 20 and exposed aperture area are covered with acolor filter layer 21, and a conventional protective layer 22 andtransparent upper common electrode 23 are successively formed thereon,thereby completing the multi-layer structure.

The above-described lower and upper panels of the LCD are supported bycertain supporting columns, and liquid crystal is injected between them.The panels are then sealed, thereby completing the LCD.

According to the LCD as shown in FIGS. 11 to 13, the first electrodes 10of the capacitors formed on the rear glass substrate perform the role ofa secondary light shielding layer together with the first lightshielding layer 20 formed on the front glass substrate 101. Therefore,light leakage is reduced to thereby improve the contrast ratio, whichresultantly improves the display characteristics of the LCD.

FIG. 14 shows a pixel layout of a liquid crystal display according to asecond embodiment of the present invention. The liquid crystal displayas shown in FIG. 14 is the same as that shown in FIGS. 11 to 13 exceptthat the connection portion between the first electrodes 10 of theadjacent capacitors is duplicated into first and second connectionportions 14a and 14b when compared with the LCD shown in FIGS. 11 to 13.

Referring to FIG. 11, the wiring crossing portion 16 where the wiringconnection portion 14 for connecting the first electrodes 10 of theadjacent storage capacitors crosses display signal line 16 is apt to bedisconnected or the wiring connection portion 14 becomes short-circuitedwith the display signal line 16 due to the inclusion of foreign matterinto the insulating layer 2 disposed therebetween or due to a poor stepcoverage of the metal layer forming the same, which deteriorates themanufacturing yield. The liquid crystal display as shown in FIG. 14 aimsto overcome this problem.

Further, in the liquid crystal display as shown in FIG. 14, due to theduplication of the wiring connection portions 14a and 14b, wiringcrossing portions 16a and 16b are also increased in number to therebyincrease the wiring resistance and the parasitic capacitance. Thisproblem can be solved by equalizing the overall line width (sum of linewidths) of the first and second wiring connection portions 14a and 14bwith the line width of the wiring connection portion 14 in FIG. 11.

The liquid crystal display as shown in FIG. 14 can be manufactured inthe same manner as explained with reference to FIGS. 11 to 13 exceptthat when forming first electrodes 10 of the storage capacitors in thering-type structure, first and second wiring connecting portions 14a and14b are also formed so as to be connected between first electrodes 10 ofadjacent capacitors.

FIG. 15 is a schematic diagram showing an operational principle forexplaining the effect of the present invention, which illustrates howthe two-fold wiring connection portions 14a and 14b can repair defectssuch as disconnections and shorting occurring in the crossing portionsof the first and second wiring connection portions 14a and 14b anddisplay signal lines 5a.

Here, a reference numeral 18 designates a single wiring for connectingthe first electrode of the storage capacitor to the driving IC circuit(not shown). Reference numerals 14a' and 14b' designate the two-foldlines for driving the first electrodes of the storage capacitorsconnected by first and second wiring connection portions 14a and 14b,respectively. An arrow designates signal current flow when only one offirst and second wiring connection portions 14a and 14b is disconnectedor short-circuited, and reference numerals 5a designate the displaysignal lines. In a portion A, first wiring connection portion 14a isdisconnected at the crossing portion of a first wiring connectionportion 14a and a display signal lines 5a. In a portion B, both firstand second wiring connection portions 14a and 14b are disconnected. Aportion C shows a state where a short circuit occurs between the secondwiring connection portion 14b and a display signal line 5a. A portion Dshows the repaired state of the short circuit in portion C.

That is, since only portion B is fatally flawed in that the first andsecond wiring connection portions both exhibit open circuits, theoverall occurrence of such fatal disconnection defects is decreased.Also, by cutting the driving line for the capacitor at both sides of thecrossing portion of the wirings in portion C by means of a laser beam,the short circuits can be repaired since the wiring connection portionsare doubled.

In the liquid crystal display as shown in FIGS. 11 to 14, the firstelectrodes 10 of the storage capacitors in each pixel region areconnected in a row direction. That is, the wiring connection portionsare formed so as to cross the display signal lines and to be parallelwith the scanning signal lines. The first electrodes of the storagecapacitors and the scanning signal lines can be simultaneously formed byusing the same material and patterning a conductive layer, whichsimplifies the manufacturing process.

However, the first electrodes of the storage capacitors in each pixelregion may be formed so as to be connected in a column direction. Here,the wiring connection portions cross the scanning signal lines and aremade to be parallel with display signal lines. However, the wiringconnection portions should be electrically isolated from the scanningsignal lines. Therefore, the scanning signal lines and the firstelectrodes of the storage capacitors should be formed by two separateprocesses. However, it should be noted that this does not depart fromthe spirit and scope of the present invention.

According to the embodiments of the present invention as describedabove, the first electrodes of the capacitor can be formed by a simplechange of the pattern when forming the scanning signal lines or whenforming the bonding pads without requiring an additional process steps,to thus simplify the processing. Moreover, the first electrode is formedto be a ring-type which can utilize a maximum pixel area, therebyenhancing the aperture ratio of the LCD. Furthermore, since the firstelectrode of the storage capacitor serves as an additional lightshielding layer, the contrast ratio and the effectiveness of the lightusage are greatly enhanced. Further, forming the first electrodes of thestorage capacitors as an independent wiring type improves the degree offreedom concerning the selection of the driving pulse signal of theliquid crystal display, and it reduces the R-C delay. Due to thereduction of the delay, the liquid crystal display can be applied to alarge panel device wherein a uniform image can not easily be achieveddue to the delay, and to a TV panel for full color operation by ananalog signal. Additionally, duplicating the connecting portions forconnecting the first electrodes of the capacitor to each other, candecrease and repair the defects due to disconnection and shorting of thedriving lines for the first electrodes occurring in the wiring crossingportions of the wirings, thereby being capable of greatly enhancing theyield of manufactured LCDs.

FIG. 16 shows a pixel layout of a liquid crystal display according to athird embodiment of the present invention. Here, the same referencenumerals as in the foregoing drawings designates the same components asthose in the foregoing drawings.

In FIG. 16, a single pixel region is illustrated. In a complete LCD,rows of a number of scanning signal lines 1 and orthogonal columns ofdisplay signal lines 5a are arranged in a matrix configuration on atransparent substrate. Thus, pixels are formed in the regions bounded bythese two kinds of lines. In each pixel region, a transparent pixelelectrode 4 is provided. As can be seen in FIG. 16, scanning signal line1 partly overlaps pixel electrode 4 to form an additional capacitancetype capacitor. Reference numeral 10c denotes the overlapping portion ofa scanning signal line 1 which forms a first electrode of an additionalcapacitance type capacitor. Further, an independent wiring 11a isprovided so as to crossing the center portion of the pixel region in asingle wiring form with an insulating layer interposed therebetween. Theoverlapping portion of the independent wiring 11a with the pixelelectrode 4 forms a storage capacitance type capacitor. Referencenumeral 10d denotes the overlapping portion of the independent wiring11a which forms the first electrode of the capacitor.

In the above liquid crystal display, a TFT using a protruding portion ofthe scanning signal line 1 as a gate electrode and using a protrudingportion of the display signal line 5a as a drain electrode is formednear the crossing portion of the scanning signal line 1 and the displaysignal line 5a as a switching device for applying an electrical signalto the pixel electrode 4 via display signal line 5a. Instead of the TFT,a thin film diode (TFD), for example, a metal insulator metal (MIM)device having two terminals, may be used, as mentioned above. In themeantime, the area defined by the dotted line in the pixel electrode 4denotes an aperture defined by the light shielding layer (black matrix)formed on the upper substrate of the liquid crystal display panel.

FIG. 17 is a cross-sectional view taken along line F-F' of FIG. 16 whichshows the lower substrate of the liquid crystal display panel. Withreference to FIG. 17, one embodiment of a method for manufacturing aliquid crystal display as shown in FIG. 16 will be explained below.

First, after preparing a rear glass substrate 100 of the liquid crystaldisplay, a pad metal layer is formed thereon and then patterned to formbonding pads (not shown) for bonding display signal line 5a and scanningsignal lines 1 to an external driving circuit. Here, the pad metal layeris formed by depositing chromium to a thickness of approximately 2,000Å. Thereafter, aluminum is deposited to a thickness not more than 4,000Å on the front surface of the rear glass substrate, to form a metallayer, which is patterned to simultaneously form scanning signal lines 1and first electrodes 10d of the storage capacitance type capacitors.Here, each scanning signal line 1 is formed so as to have a protrudingportion which extends into each pixel region. The protruding portionsare used as gate electrodes of thin film transistors. Also, firstelectrodes 10c of additional capacitance type capacitors which areconstituted by a portion of the scanning signal lines 1 and oppose thepixel electrodes 4 (which are formed in a subsequent step), aresimultaneously formed.

For simplifying the manufacturing process, first electrodes 10d of thestorage capacitance type capacitor may be formed by using the samematerial as the pad material. That is, after forming the pad metallayer, the first electrodes 10d are simultaneously formed whenpatterning the pad metal layer. Alternatively, first electrodes 10d ofthe storage capacitance type capacitor may be formed via a differentstep from the step for forming the scanning signal lines 1, by using adifferent metal from that for scanning signal line 1. When forming thefirst electrodes 10d of the storage capacitance type capacitor using anopaque metal, the aperture area is reduced as much as the area occupiedby the first electrodes 10d. Therefore, forming the first electrodes 10dusing a transparent conductive material such as ITO is preferable eventhough the first electrodes 10d are formed by an additional process.

When scanning signal lines 1 or first electrodes 10c and 10d are made ofaluminum, using an anodic oxide method, the surfaces of lines orelectrodes can be covered by an aluminum oxide film (Al₂ O₃) whosethickness is not more than 2,000 Å to enhance the electricalcharacteristic of the pixel electrodes 4, crossing portions 16 and inthe TFTs.

Then, using a chemical vapor deposition (CVD) method, an insulatinglayer 2 comprising silicon nitride (SiNx) and a semiconductor layer 3comprising an amorphous hydride silicon (a-Si:H) are formed tothicknesses of about 3,000 Å or less and 2,000 Å or less, respectively.At this time, a-Si:H doped with an N-type impurity (n⁺ a-Si:H) isdeposited to form an ohmic layer having a thickness of approximately 500Å on the previously deposited a-Si:H. Further, when the TFT is formed byusing an etching blocking layer, a silicon nitride layer may be formedon the semiconductor layer as an etching blocking layer. Thereafter, thesemiconductor layer 3 is patterned so as to define areas in which theswitching devices will be placed near the portions where scanning signallines 1 and display signal lines 5a cross each other.

Successively, the insulating layer 2 on the bonding pads (not shown) isremoved, and a transparent conductive material, e.g., ITO, is depositedto a thickness of about 500 Å or below via a sputtering method, andpatterned to thereby form pixel electrodes 4 on the insulating layer 2(i.e. on the same plane as the semiconductor layer 3). At this time,each pixel electrode 4 is patterned to partially overlap its associatedfirst electrode 10c of the storage capacitor formed in the foregoingstep by a predetermined width interposing the insulating layer 2therebetween. An additional capacitance type capacitor is formed betweenthe first electrode 10c and the pixel electrode 4 in each pixel area byinterposing the insulating layer 2 as a dielectric material therebetweenand a storage capacitance type capacitor is formed between the firstelectrode 10d and the pixel electrode 4 in each pixel region, so that avoltage signal input through display signal line 5a is maintained for apredetermined time period until the succeeding input signal arrives.

Then, chromium and aluminum are successively deposited on the wholesurface of the substrate to a thicknesses of about 500 Å or less and5,000 Å or less, respectively, via a sputtering method, and thenpatterned to form display signal lines 5a, sources 5b and the drainelectrodes of the TFT. Thereafter, a protective layer comprising siliconnitride is formed on the whole surface of the substrate to a thicknessof about 4,000 Å via a CVD method. Hence, the lower panel of the LCD iscompleted. Of course, on protective layer 6, an orientation layer (notshown) may be formed in a subsequent step for the orientation of theliquid crystal; which is conventional in the LCD art.

In the meantime, the upper panel of the LCD is completed in such amanner that, after the aperture area of the LCD is defined by forming alight shielding layer on the inner surface of the transparent frontglass substrate as matrices along the periphery of each pixel area, thelight shielding layer and exposed aperture area are covered with a colorfilter layer, and a conventional protective layer and transparent uppercommon electrode are successively formed thereon, thereby completing themulti-layer structure.

The above-described lower and upper panels of the LCD are supported bycertain supporting columns, and liquid crystal is injected between them.The panels are then sealed, thereby completing the LCD.

FIG. 18 is an equivalent circuit diagram of the liquid crystal displayas shown in FIGS. 16 and 17. In the unit pixels defined by the scanningsignal lines 1 and the display signal lines 5a, there exist capacitancessuch as Ccr (the capacitance formed at the crossing portion of ascanning signal line 1 and display signal line 5a), Cst₂ (thecapacitance formed between the pixel electrode 4 and the first electrode10d of the opposing storage capacitance type capacitor), Clc (thecapacitance formed between the pixel electrode 4 and the liquidcrystal), Cadd₂ (the capacitance formed between the pixel electrode 4and the first electrode 10c of the additional capacitance typecapacitor), Cds (the capacitance formed between the source and drainelectrodes of the thin film transistor), Cgs (the capacitance formedbetween the gate and source electrodes) and Cgd (the capacitance formedbetween the gate and drain electrodes).

Generally, in order to secure image uniformity in an active matrix typeliquid crystal display, the voltage of a first signal applied through adata line in the writing operation should be held constant for a certaintime until a second signal is received, when assuming that a storagecapacitor having a predetermined capacitance is formed in parallel witha liquid crystal cell, the following equation will be obtained from thecircuits of FIGS. 3, 6 and 18.

    Ca=Cs=Cadd.sub.2 +Cst.sub.2                                (3)

Further, the capacitance of the scanning signal line (Cssl) according tothe third embodiment of the present invention is as follows.

    Cssl=Cin+1/[(1/Cadd.sub.2)+{1/(Clc+Cgd+Cst.sub.2)}]        (4)

As can be seen from the above equation, the gate wiring capacitance ofthe present embodiment is smaller than that of an LCD which has only anadditional capacitance type capacitor as shown in FIG. 4.

In the meantime, in order to optimize the ratio of the gate wiringcapacitance Cadd₂ due to the additional capacitance type capacitor withrespect to the gate wiring capacitance Cst₂ due to the storagecapacitance type capacitor, a trade-off is performed by considering theimprovement in the aperture ratio obtainable by employing the additionalcapacitance type capacitor and the reduction in the gate wiringcapacitance obtainable by employing the storage capacitance typecapacitor.

An example of the trade-off will be illustrated as follows. In a15"-sized liquid crystal display panel of the Engineering Work StationStandard having 1280×1024 pixels, when the pixel size is 80 μm×240 μm,the gate wiring resistance (R) is 3.41 KΩ, the capacitance (Ccr) of thewiring crossing portion of the scanning signal line and the displaysignal line is 0.04 pF, the capacitance of the liquid crystal. (Clc) is0.16 pF, the sum of the additional capacitance (Cadd₂) and the storagecapacitance (Cst₂) is 0.3 pF, the capacitance (Cgd) between the gateelectrode and the drain electrode is 0.02 pF and the capacitance (Cgs)between the gate electrode and the source electrode is 0.02 pF, the RCtime constant in accordance with the ratio of the additional capacitance(Cadd₂) with respect to the storage capacitance (Cst₂) is as follows.

                  TABLE 1                                                         ______________________________________                                                                  Ratio with respect to                                           RC time constant                                                                            the storage capacitor                               Cst.sub.2 (%):Cadd.sub.2 (%)                                                              (μsec)     type                                                ______________________________________                                         0:100      2.51          2.42                                                10:90       2.58          2.49                                                20:80       2.61          2.51                                                30:70       2.58          2.49                                                40:60       2.51          2.42                                                50:50       2.38          2.30                                                60:40       2.21          2.13                                                70:30       1.99          1.92                                                80:20       1.72          1.66                                                90:10       1.40          1.35                                                100:0       1.03          1.00                                                ______________________________________                                    

In the above Table 1, the ratio of Cst₂ to Cadd₂ can be defined as theratio of the area occupied by the first electrode of the storagecapacitance type capacitor with respect to the area occupied by thefirst electrode of the additional capacitance type capacitor. As can beseen in Table 1, it can be noted that when the ratio of the storagecapacitance to the additional capacitance is more than 80:20, an RC timeconstant less than 1.66 times as much as that of the conventionalstorage type liquid crystal display results, which is efficient.

In the meantime, many variations concerning the additional capacitancetype capacitor and the storage capacitor with respect to the thirdembodiment of the present invention are possible.

For example, the first electrode of the additional capacitance typecapacitor may be formed as a ring type electrode as shown in FIG. 7.FIG. 19 shows a pixel layout of the liquid crystal display according toa fourth embodiment of the present invention.

Referring to FIG. 19, the liquid crystal display according to thisembodiment is characterized in that first electrode 10c of theadditional capacitance is formed in a ring shape so as to partiallyoverlap along the periphery of the pixel electrode 4. The firstelectrode 10c is formed in a ring shape in the pixel region between thefirst electrode 10d of the additional capacitance type capacitor and thescanning signal line 1 for operating the adjacent pixel electrode. Thepresent embodiment reflects the improvement of the aperture ratio whichcan be achieved by the ring type first electrode of the LCD as shown inFIG. 7. The area defined by the dotted line in the pixel electrode 4denotes an aperture area defined by the light shielding layer (blackmatrix) formed on the upper panel of the liquid crystal display panel.Further, the liquid crystal display in the present embodiment onlydiffers from the liquid crystal display as shown in FIG. 16 in that thefirst electrode 10c of the additional capacitor is formed as a ring typeelectrode between the first electrode 10d of the storage capacitor andthe scanning signal line 1 for operating the adjacent pixel electrode.The liquid crystal display as shown in FIG. 19 can be manufactured inthe same manner as when forming the liquid crystal display as shown inFIG. 16, except that when forming the first electrode 10c of theadditional capacitor, a mask having the same layout as shown in FIG. 19is used. Optimization of the ratio between the additional capacitanceand the storage capacitance is performed as mentioned with reference tothe above Table 1.

In the meantime, FIG. 19 shows a pixel layout wherein the firstelectrode of the additional capacitor is formed as a ring typeelectrode. However, the first electrode 10d of the storage capacitor mayformed as a ring type electrode instead of the first electrode 10c ofthe additional capacitor, as shown in FIG. 11. In such a case, themanufacturing process is the same as in forming the liquid crystaldisplay as shown in FIG. 16, except that when forming the firstelectrode 10d of the storage capacitor, a mask forming the firstelectrode 10d of the storage electrode which has the layout surroundingthe pixel electrode 4 along the periphery thereof is used. Also,optimization of the ratio between the additional capacitance and thestorage capacitance is performed as mentioned with reference to theabove Table 1.

Further, according to another embodiment of the present invention, boththe first electrode 10c of an additional capacitor and the firstelectrode 10d of the storage capacitor may be formed as a ring typeelectrode so as to surround along the periphery of the pixel electrode4.

Meanwhile, the liquid crystal display according to a third embodiment ofthe present invention represents an improvement in displaycharacteristics, i.e., a better aperture ratio, increased contrastratio, etc. However, due to the introduction of foreign matter or a weakinsulating film at wiring crossings (the intersections of scanningsignal lines 1 and display signal lines 5a or the intersections ofdisplay signal lines 5a and independent wirings 11a for connecting thefirst electrodes 10d of the storage capacitance type capacitors), wiringdisconnections in scanning signal lines 1 and/or short circuits betweenscanning signal lines 1 and display signal lines 5a or between displaysignal lines 5a and independent wirings 11a for connecting the firstelectrodes 10d of the storage capacitance type capacitors may occur, tothereby significantly lower the yield of manufactured liquid displays.

In order to solve the problems of wiring fractures in scanning signallines 1 and/or short circuits between scanning signal lines 1 anddisplay signal lines 5a without reducing the aperture ratio and thecontrast ratio, the scanning signal lines and the independent wiringsfor driving the first electrodes 10d of the storage capacitors may beduplicated as shown in FIGS. 9, 10 and 14. FIG. 20 show a pixel layoutaccording to a fifth embodiment of the present invention wherein thescanning signal lines and the independent wirings for driving the firstelectrodes of the storage capacitors are duplicated.

In the liquid crystal display as shown in FIG. 20, each scanning signalline is duplicated into a first scanning signal line 1a and a secondscanning signal line 1b. The first electrode 10c of the additionalcapacitance type capacitor which is electrically connected to firstscanning signal line 1a, is formed so as to surround the pixel electrode4 along the peripheral portion thereof between the second scanning line1b and the first scanning signal line 1a for driving the adjacent pixelelectrode. Also, each independent wiring for driving the firstelectrodes of the storage capacitance type capacitors is duplicated intoa first independent wiring 1c and a second independent wiring 1d. Thefirst electrode of the storage capacitance type capacitor is formed soas to surround the pixel electrode 4 along the peripheral region thereofbetween the first and second independent wirings 1c and 1d.

In the liquid crystal display as shown in FIG. 20, disconnections and/orshort circuits which may occur at the wiring crossing portions, can beeasily repaired. The liquid crystal display as shown in FIG. 20 can bemanufactured in the same manner as when manufacturing the liquid crystaldisplays as shown in FIGS. 16 and 19 by simply altering the layout forforming the first electrodes of the additional capacitors and the firstelectrodes of the storage capacitors. Also, optimization of the ratiobetween the additional capacitance and the storage capacitance may beperformed as mentioned with reference to the above Table 1.

The ratio of the storage capacitance with respect to the additionalcapacitance can be varied in order to improve the aperture ratio and/orin order to reduce the capacitance of the scanning signal lines.Further, the first electrodes of the additional capacitance typecapacitors and the storage capacitance type capacitors can be formed soas to have various shapes. Additionally, the manufacturing method of theliquid crystal display as described above can be varied according to theselection of the material for forming the first electrodes of thestorage capacitance type capacitors and the additional capacitance typecapacitors.

According to the third to fifth embodiments of the present invention,the gate wiring capacitance can be decreased when compared to the liquidcrystal display having the additional capacitance type capacitors so asto reduce the RC time constant. Therefore, a liquid crystal displayhaving a uniform image can be obtained. Further, the aperture ratio isimproved when compared to a liquid crystal display having the storagecapacitance type auxiliary capacitors so that a liquid crystal displaydevice having improved brightness and/or contrast ratio can be realized.

According to the fifth embodiment of the present invention as describedabove, the redundancy connecting portions for connecting the firstelectrodes of the storage capacitors or the two-fold scanning signallines are formed by a simple change of the pattern without requiring anadditional process, to thus simplify the processing. Since redundancyconnecting portions are formed for connecting the first electrodes ofthe capacitors to each other, or the scanning signal lines are doubled,the defects of disconnection and shorting of the scanning signal linesoccurring in the crossing portion of the wirings can be decreased andrepaired, thereby being capable of greatly enhancing the yield ofmanufactured LCDs.

While the present invention has been particularly shown and describedwith reference to particular embodiments thereof, it will be understoodby those skilled in the art that various changes in form and details maybe effected therein without departing from the spirit and scope of theinvention as defined by the appended claims.

What is claimed is:
 1. A liquid crystal display device comprising:atransparent substrate; a plurality of scanning signal lines and aplurality of display signal lines intersecting said plurality ofscanning signal lines, arranged in a matrix configuration on a surfaceof said transparent substrate and defining a plurality of pixel regionseach bounded by a pair of said plurality of scanning signal lines and apair of said plurality of display signal lines; a plurality of pixelelectrodes corresponding respectively to said plurality of pixelregions; a plurality of switching devices corresponding respectively tosaid plurality of pixel regions, each of said plurality of switchingdevices being connected to a corresponding one of said plurality ofdisplay signal lines and a corresponding one of said plurality of pixelelectrodes; a plurality of first electrodes within each of saidplurality of pixel regions forming a respective plurality of additionalcapacitance type capacitors in conjunction with said plurality of pixelelectrodes thereof; a plurality of ring-type electrodes disposedrespectively within each of said plurality of pixel regions so as toface said corresponding one of said plurality of pixel electrodes and soas to surround said corresponding one of said plurality pixelelectrodes, for forming a plurality of storage capacitance typecapacitors respectively with each of said plurality of pixel electrodes,said plurality of ring-type electrodes being driven independently fromsaid plurality of scanning signal lines and said plurality of displaysignal lines; and a plurality of wiring connecting portions connectingadjacent ones of said plurality of ring-type electrodes.
 2. A liquidcrystal display device as claimed in claim 1, further comprising:abonding pad layer for connecting said plurality of scanning signal linesand said plurality of display signal lines to a driving circuit; saidplurality of ring-type electrodes and said bonding pad are comprised ofa same material.
 3. A liquid crystal display device as claimed in claim1, wherein:said plurality of ring-type electrodes and said plurality ofscanning signal lines are comprised of a same material.
 4. A liquidcrystal display device as claimed in claim 3, wherein:said plurality ofring-type electrodes and said plurality of scanning signal lines arecomprised of at least one opaque conductive metal selected from a groupconsisting of aluminum, chromium, molybdenum and tantalum.
 5. A liquidcrystal display device as claimed in claim 4, wherein:said plurality ofring-type electrodes and said plurality of scanning signal lines have astacked structure comprised of at least two metals.
 6. A liquid crystaldisplay device as claimed in claim 1, wherein:said plurality of wiringconnecting portions cross said plurality of display signal lines.
 7. Aliquid crystal display device as claimed in claim 6, wherein:two of saidplurality of wiring connecting portions are connected to each of saidplurality of ring-type electrodes.
 8. A liquid crystal display device asclaimed in claim 1, wherein:said plurality of ring-type electrodes andsaid plurality of scanning signal lines are different conductive layers.9. A liquid crystal display device as claimed in claim 8, wherein:saidplurality of wiring connecting portions are cross said plurality ofdisplay signal lines.
 10. A liquid crystal display device as claimed inclaim 9, further comprising:an insulating layer interposed between saidplurality of ring-type electrodes and said plurality of scanning signallines to isolate said plurality of ring-type electrodes from saidplurality of scanning signal lines.
 11. A liquid crystal display deviceas claimed in claim 9, wherein:two of said plurality of wiringconnecting portions are connected to each of said plurality of ring-typeelectrodes.
 12. A liquid crystal display device as claimed in claim 1,wherein:said plurality of switching devices each comprises a thin filmtransistor.
 13. A liquid crystal display device as claimed in claim 12,wherein each of said thin film transistors comprises:a gate electrodeformed of a portion of a corresponding one of said plurality of scanningsignal lines; a drain electrode formed of a projecting portion of acorresponding one of said plurality of display signal lines; a sourceelectrode overlapping a portion of a corresponding one of said pluralityof pixel electrodes; an insulating layer on said gate electrode; and asemiconductor layer formed on said insulating layer and connecting saiddrain electrode to said source electrode.
 14. A liquid crystal displaydevice as claimed in claim 13, wherein:each of said thin filmtransistors is inversely staggered and formed on a crossing point ofsaid corresponding one of said plurality of scanning signal lines andsaid corresponding one of said plurality of display signal lines.
 15. Aliquid crystal display device as claimed in claim 13, wherein:said gateelectrode, said drain electrode, and said semiconductor layer of saidthin film transistor are formed outside a boundary of a correspondingone of said plurality of pixel electrodes.
 16. A liquid crystal displaydevice as claimed in claim 13, wherein:said source electrode of saidthin film transistor overlays a portion of a corresponding one of saidplurality of ring-type electrodes.
 17. A liquid crystal display deviceas claimed in claim 1, wherein:said plurality of ring-type electrodespartially overlap along an overall periphery of respective ones of saidplurality of pixel electrodes.
 18. A liquid crystal display device asclaimed in claim 17, wherein:a portion of a periphery of each of saidplurality of ring-type electrodes overlaps a portion of said respectiveone of said plurality of pixel electrodes by a predetermined width. 19.A liquid crystal display device as claimed in claim 1, furthercomprising:an insulating layer; said plurality of ring-type electrodesand said plurality of scanning signal lines being disposed substantiallyon a first horizontal plane; said plurality of pixel electrodes and saidplurality of display signal lines being disposed substantially on asecond horizontal plane; and said insulating layer spacing said firsthorizontal plane apart from said second horizontal plane.
 20. A liquidcrystal display comprising:a front glass substrate having an innersurface and an outer surface; a rear glass substrate having an innersurface and an outer surface, said rear glass substrate being inparallel with said front glass substrate and being separated therefromby a predetermined distance, said inner surface of said rear glasssubstrate opposing said inner surface of said front glass substrate; aplurality of scanning signal lines and a plurality of display signallines intersecting said plurality of scanning signal lines, arranged onsaid inner surface of said rear glass substrate in a matrix defining aplurality of pixel areas each bounded by a pair of said plurality ofscanning signal lines and a pair of said plurality of display signallines; a plurality of pixel electrodes corresponding respectively tosaid plurality of pixel areas; a plurality of switching devicescorresponding respectively to said plurality of pixel areas, each ofsaid plurality of switching devices being connected to a correspondingone of said plurality of display signal lines and a corresponding one ofsaid plurality of pixel electrodes; a plurality of first electrodesforming a plurality of additional capacitance type capacitorsrespectively within each of said plurality of pixel areas; a pluralityof second electrodes arranged respectively within said plurality ofpixel areas and oppositely enclosing a corresponding one of saidplurality of pixel electrodes to form a respective one of a plurality ofstorage type capacitors in conjunction with said corresponding one ofsaid plurality of pixel electrodes, said plurality of second electrodesbeing driven independently from said plurality of scanning signal linesand said plurality of display signal lines; a plurality of wiringconnecting portions connecting said plurality of second electrodes ofadjacent ones of said plurality of pixel areas; a light-shielding matrixlayer on said inner surface of said front glass substrate aligned withsaid plurality of pixel areas, said light-shielding matrix layerdefining a plurality of light-transmitting aperture areas therein; acolor filter layer on said inner surface of said front glass substrateand including a plurality of light transmitting areas respectivelycovering said plurality of light-transmitting aperture areas and saidlight-shielding matrix layer; a transparent electrode formed on saidcolor filter layer; and a liquid crystal layer between said front glasssubstrate and said rear glass substrate; at least one of said pluralityof first electrodes or said plurality of second electrodes beingring-shaped.
 21. A liquid crystal display as claimed in claim 20,further comprising:a first protective layer sandwiched between saidcolor filter layer and said transparent electrode.
 22. A liquid crystaldisplay as claimed in claim 20, further comprising:a second protectivelayer covering said inner surface of said rear glass substrate.
 23. Aliquid crystal display as claimed in claim 20, wherein:a border of eachof said plurality of light-transmitting aperture areas defined by saidlight-shielding matrix layer is substantially in vertical alignment withan inner periphery of a corresponding one of said plurality of secondelectrodes; said plurality of second electrodes functioning as asecondary light shielding layer for decreasing light leakage other thanlight permitted to be passed through said plurality oflight-transmitting aperture areas.
 24. A liquid crystal display asclaimed in claim 20, wherein:light projecting to said plurality oflight-transmitting aperture areas via said rear glass substrate definesa respective plurality of virtual aperture areas, and said plurality ofsecond electrodes do not extend into said plurality of virtual apertureareas.
 25. A method for manufacturing a liquid crystal display having atransparent substrate, a plurality of scanning signal lines intersectinga plurality of display signal lines and forming a matrix configurationon a surface of said transparent substrate defining a plurality of pixelregions each bounded by a pair of said plurality of scanning signallines and a pair of said plurality of display signal lines, a pluralityof pixel electrodes corresponding respectively to said plurality ofpixel regions, a plurality of switching devices correspondingrespectively to said plurality of pixel regions, and a plurality ofelectrodes respectively within said plurality of pixel regions, saidplurality of electrodes being independent from said plurality ofscanning signal lines and said plurality of display signal lines, saidmethod comprising steps of:forming a first metal layer on a transparentsubstrate; patterning said first metal layer to form bonding pads forconnecting inner elements to an outer circuits, to form said pluralityof electrodes of a respective plurality of storage capacitance typecapacitors in respective ones of said plurality of pixel regions, and toform at least one wiring connecting portion for connecting adjacent onesof said plurality of electrodes; forming a second metal layer on theresultant structure having said bonding pads and said plurality ofelectrodes thereon; patterning said second metal layer to form saidplurality of scanning signal lines at regular intervals, and to form aplurality of electrodes of a respective plurality of additionalcapacitance type capacitors respectively within said plurality of pixelregions with an insulating layer therebetween; forming an insulatinglayer on a surface of the resultant structure; forming a semiconductorlayer on said insulating layer; patterning said semiconductor layer toleave only a portion of said semiconductor layer around a portion ofsaid plurality of scanning signal lines; forming a transparentconductive layer on a surface of the resultant structure; patterningsaid transparent conductive layer to form said plurality of pixelelectrodes respectively opposed to said plurality of electrodescorresponding to said plurality of storage capacitance type capacitoralong a periphery thereof; forming a third metal layer on the resultantstructure; and patterning said third metal layer to form said pluralityof display signal lines regularly arranged and intersecting saidplurality of scanning signal lines, and to form respective source anddrain electrodes of a thin film transistor on said semiconductor layer.26. A liquid crystal display device comprising:a transparent substrate;a plurality of first scanning signal lines and an intersecting pluralityof display signal lines arranged in a matrix configuration on thesurface of said transparent substrate, to thereby define a plurality ofpixel regions each bounded by a pair of first scanning signal lines anda pair of display signal lines; a pixel electrode in each pixel region;a switching device in each pixel region and connected with acorresponding display signal line and the pixel electrode of therespective pixel region; a first electrode of an additional capacitancetype capacitor within each pixel region, for forming an additionalcapacitance type capacitor in conjunction with the pixel electrodethereof and arranged so as to face a portion of each pixel electrodewith an insulating layer interposed therebetween; a first electrode of astorage capacitance type capacitor within each pixel region formed byinterposing an insulating layer, for forming a storage capacitance typecapacitor in conjunction with the pixel electrode thereof and arrangedso as to face a portion of each pixel electrode, said first electrodesbeing independent from said scanning signal lines; and a firstindependent wiring connecting said first electrodes of adjacent storagecapacitance type capacitors.
 27. A liquid crystal display as claimed inclaim 26, wherein said first electrode of the storage capacitance typecapacitor and said first electrode of said additional capacitance typecapacitor comprise the same material as said scanning signal lines. 28.A liquid crystal display as claimed in claim 26, wherein said firstelectrode of said storage capacitance type capacitor is comprised of aconductive transparent material.
 29. A liquid crystal display as claimedin claim 26, wherein said scanning signal lines are formed so as to haveportions protruding into said pixel regions so that said protrudingportions partially overlap said pixel electrodes to form said firstelectrodes of said additional capacitance type capacitors.
 30. A liquidcrystal display as claimed in claim 26, wherein said first electrode ofsaid storage capacitance type capacitor and said first electrode of saidadditional capacitance type capacitor are formed of a single wiringtype.
 31. A liquid crystal display as claimed in claim 20, wherein saidfirst electrode of said additional capacitance type capacitor is formedin a ring type which surround the peripheral region of said pixelelectrode, said first electrode of said additional capacitance typecapacitor being formed between said scanning signal line for drivingsaid pixel electrode of adjacent pixel region and said first electrodeof the storage capacitance type capacitor.
 32. A liquid crystal displayas claimed in claim 31, further comprising a redundancy connectionportion for connecting said first electrode to the adjacent firstelectrode.
 33. A liquid crystal display as claimed in claim 26, whereinsaid first electrode of the storage capacitance type capacitor is formedin a ring type which surrounds the peripheral region of said pixelelectrode, said first electrode of said storage capacitance typecapacitor being formed between said scanning signal line and said firstelectrode of the additional capacitance type capacitor.
 34. A liquidcrystal display as claimed in claim 33, further comprising a secondindependent wiring for connecting the first electrodes of the adjacentstorage capacitance type capacitors.
 35. A liquid crystal display asclaimed in claim 26, wherein said first electrode of the storagecapacitance type capacitor comprises the same material as that ofbonding pads formed on said transparent substrate for connecting saidscanning signal lines to an outer driving circuit.
 36. A liquid crystaldisplay as claimed in claim 26, Wherein the ratio of the storagecapacitance with respect to the additional capacitance is greater than80:20.
 37. A liquid crystal display as claimed in claim 26, wherein saidswitching device comprises a thin film transistor.
 38. A liquid crystaldisplay device comprising:a transparent substrate; a plurality of firstscanning signal lines and display signal lines arranged in a matrixconfiguration on a surface of said transparent substrate, to therebydefine a plurality of pixel regions each bounded by a pair of firstscanning signal lines and a pair of display signal lines: a pixelelectrode in each pixel region; a switching device in each pixel regionand connected with a corresponding display signal line and the pixelelectrode; a first electrode of an additional capacitance type capacitordisposed within pixel region so as to face the pixel electrode, forforming an additional capacitor with the pixel electrode with aninsulating layer interposed therebetween, said first electrode of saidadditional capacitance type capacitor being formed in a ring shape whichsurround the peripheral region of said pixel electrodes; at least oneredundancy connection portion for connecting said first electrodes ofthe additional capacitance type capacitors of adjacent pixel regions; afirst electrode of a storage capacitance type capacitor disposed withinsaid pixel region so as to face the pixel electrode with an insulatinglayer disposed therebetween, for forming storage capacitor with thepixel electrode, said first electrode being independent from saidscanning signal lines, said first electrode of the storage capacitancetype capacitor being formed in a ring shape which surrounds theperipheral region of said pixel electrode, said first electrode of saidstorage capacitance type capacitor being formed between thecorresponding scanning signal line and said first electrode of theadditional capacitance; a first independent wiring connecting said firstelectrodes of the storage capacitance type capacitors of adjacent pixelregions; and a second independent wiring for connecting said firstelectrodes of the storage capacitance type capacitors of adjacent pixelregions.
 39. A liquid crystal display comprising:a front glass substratehaving inner and outer surfaces; a rear glass substrate having inner andouter surfaces, paralleling said front glass substrate and separatedtherefrom by a predetermined distance to allow its inner surface tooppose said inner surface of said front glass substrate; a plurality ofscanning signal lines and display signal lines arranged on said innersurface of said rear glass substrate as matrixes for defining aplurality of pixel areas each bounded by means of a pair of saidscanning signal lines and a pair of said display signal lines; a pixelelectrode within said pixel area; a switching device within said pixelarea for connecting a corresponding display signal line to said pixelelectrode; a first electrode of an additional capacitance type capacitordisposed within said pixel region so as to face a portion of the pixelelectrode with an insulating layer interposed therebetween, for formingan additional capacitance type capacitor; a first electrode of a storagecapacitance type capacitor disposed within said pixel region so as toface a portion of the pixel electrode with an insulating layerinterposed therebetween, for forming a storage capacitance typecapacitor with the pixel electrode, said first electrode beingindependent from said scanning signal lines; a light-shielding layermatrix formed on said inner surface of said front glass substrate andaligned with each pixel area for defining a light-transmitting aperturearea; a color filter layer on said inner surface of said front glasssubstrate and including a light transmitting area covering saidlight-transmitting aperture area and said light-shielding layer; atransparent electrode formed on said color filter layer; and a liquidcrystal layer between said front and rear glass substrate.
 40. A methodfor manufacturing a liquid crystal display having a liquid crystaldisplay having a transparent substrate; a plurality of scanning signallines and intersecting display signal lines arranged in a matrixconfiguration on a surface of said transparent substrate to therebydefine a plurality of pixel regions each bounded by a pair of scanningsignal lines and a pair of display signal lines; a pixel electrode ineach pixel region; a switching device in each pixel region; and a firstelectrode of a storage type capacitor within each pixel region beingindependent from the scanning signal lines and the display signal lines,said method comprising the steps of:forming a first metal layer on saidtransparent substrate; patterning said first metal layer to form bondingpads for connecting inner elements to an outer circuit; forming a secondmetal layer on the resultant structure having the bonding pads thereon;patterning said second metal layer to form said scanning signal lines ina regular arrangement, a first electrode of additional capacitance typecapacitor within said pixel region so as to face a portion of the pixelelectrode, for forming an additional capacitance type capacitor with aninsulating layer interposed therebetween and said first electrode of thestorage capacitance type capacitor disposed within said pixel region soas to face a portion of said pixel electrode, for forming storagecapacitors with the pixel electrodes with said insulating layerinterposed therebetween; successively forming an insulating layer and asemiconductor layer on the surface of the resultant structure;patterning said semiconductor layer to leave the semiconductor layeronly around a portion of said scanning signal lines; forming atransparent conductive layer on the surface of the resultant structure;patterning said transparent conductive layer to form said pixelelectrode to oppose to said first electrode of said storage capacitoralong a periphery thereof; and forming a third metal layer on theresultant; patterning said third metal layer to form said plurality ofdisplay signal lines regularly arranged while intersecting said scanningsignal lines, and source and drain electrodes of a thin film transistoron said semiconductor layer.
 41. A method for manufacturing a liquidcrystal display as claimed in claim 40, wherein:said plurality ofscanning signal lines and said plurality of first electrodes of storagetype capacitors are formed simultaneously by patterning said secondmetal layer.
 42. A method for manufacturing a liquid crystal display asclaimed in claim 41, wherein:said plurality of wiring connectionportions are formed so that said plurality of first electrodes ofstorage type capacitors are connected in parallel with said plurality ofscanning signal lines.
 43. A method for manufacturing a liquid crystaldisplay as claimed in claim 40, wherein:said plurality of scanningsignal lines and said plurality of first electrodes of said respectiveplurality of storage capacitors are formed by a separate patterningprocess.
 44. A method for manufacturing a liquid crystal display asclaimed in claim 43, wherein:said plurality of wiring connectionportions are formed so as to cross said plurality of display signallines.